1. Field of the Invention
This invention relates generally to the field of large stadiums, such as athletic stadiums, and in particular to stadiums in which is desired to have a natural grass activity area, such as athletic playing field.
2. Description of the Related Technology
Historically, when most professional sports stadiums were of the fully outdoor, open bowl design, growing and maintaining a natural grass playing field was not considered difficult, and was in fact the norm. This changed, however, with the advent of the large, indoor domed professional sports stadiums in the 1970s. It being impractical to grow natural grass in a domed stadium because of the lack of sunlight and natural precipitation, all of the large, domed athletic stadiums utilize artificial turf when hosting athletic events, such as baseball or football, that require a grass-like playing surface.
In recent years, however, professional athletes, their unions, and the teams and leagues themselves have begun to express a clear preference for natural grass playing fields. This is particularly true for baseball and football players in the United States. Natural grass is felt by many players to be safer, more pleasant, and less physically taxing to play on than artificial turf.
In the last few years, retractable roof stadiums have come into play with the intention of providing sufficient sunlight to the field to grow natural turf. While this has worked reasonably well in most cases, it has been difficult to aggressively grow grass. Even though the stadium roof will open, it generally does not adequately provide the two most important elements to grow grass, which are direct sunlight for a maximum period of time each day and a warm, moist environment at field level to promote growth. It is problematic that most stadiums only allow a shaft of light onto the field because the stadium support walls and other devices block the sun early in the morning and late in the afternoon. Secondly, most stadiums are air-conditioned, and since most stadiums are built in a depressed cavity below ground level, the cold air-conditioned air, even when the roof is opened, tends to linger at field level. This cool, dry air tends to inhibit the growth of grass and has caused problems in the industry.
Another factor that has been an impediment to be widespread deployment of natural grass to playing surfaces in retractable roof type stadiums is the relative difficulty in reconfiguring the exhibition area in a stadium that utilizes natural grass to an alternative purpose, such as for basketball, rodeo exhibitions, circuses and the like. Unlike artificial turf, natural grass cannot be covered for an indefinite period of time, it is difficult to temporarily move and further can cause problems of condensation in the event that a temporary surface is erected above it.
Attempts have been made to design a movable game field that can be moved from one location to another. U.S. Pat. No. 5,746,028 to DiBenedetto discloses a movable grass field that is mounted on a superstructure base that is secured to and spans a system of wheels for movement in and out of a sports stadium. To the best of the knowledge of the present inventors, such a system has never been successfully deployed in a large sports stadium. As the inventors are aware based on their widespread experience in the design and construction of very large structures, a number of practical problems are presented that have deterred the practical implementation of large mobile platforms bearing natural turf. One practical problem is that existing stadiums are designed so as to have exhibition levels that are at a predetermined elevation with respect to the surrounding seating area. It has long been felt that a movable turf platform would necessarily because of the tremendous weight of the turf and underlying soil itself need to be made so as to be prohibitively thick and bulky. In addition, vibrational characteristics are a major concern. In sports such as professional American football, for example, twenty-two large men will periodically be simultaneously exerting themselves on the field. In order for game play to be acceptable to the athletes, the field must have a solid feel to it, as if no independent platform existed. This is problematic and is also antagonistic to the requirement that the platform be as compact and unobtrusive as possible.
A need exists in the industry for an improved stadium design and method that will permit more effective growth of natural grass for a stadium, provide an acceptable surface for athletic play and that will further permit efficient reconfiguration of the stadium in the event that an alternative event not requiring natural grass is to be hosted.
Accordingly, it is an object of the invention to provide an improved stadium design and method that will permit more effective growth of natural grass for a stadium, provide an acceptable surface for athletic play and that will further permit efficient reconfiguration of the stadium in the event that an alternative event not requiring natural grass is to be hosted.
In order to achieve the above and other objects of the invention, a method of operating a stadium according to a first aspect of the invention includes steps of positioning a natural grass activity platform in a first location that is outside of the stadium, the natural grass activity platform having a surface area of natural grass that is at least 10,000 square feet and being constructed and arranged to have a characteristic frequency that is at least 6 Hz; and moving the natural grass activity platform as a complete unit to a second location that is within the stadium, the step of moving the natural grass activity platform being performed without disassembly and reassembly of the natural grass activity platform.
According to a second aspect of the invention, the convertible public exhibition facility may include a stadium having an exhibition area and a seating area that is situated about the exhibition area for permitting spectators to view activities taking place in the exhibition area; a movable natural grass activity platform that has a surface area of natural grass that is at least 10,000 square feet and is constructed and arranged to have a characteristic frequency of at least about 6 Hz; and a transport mechanism that is constructed and arranged so as to be able to move the natural grass activity platform as a complete unit from a first location outside of the stadium to a second location that is within the exhibition area.
These and various other advantages and features of novelty that characterize the invention are pointed out with particularity in the claims annexed hereto and forming a part hereof. However, for a better understanding of the invention, its advantages, and the objects obtained by its use, reference should be made to the drawings which form a further part hereof, and to the accompanying descriptive matter, in which there is illustrated and described a preferred embodiment of the invention.